Henna tattoos may seem like a good idea while you're on vacation, but as Twitter user James Colley from Cardiff, Wales, recently learned, it's still important to do your research first. During a trip to Zakynthos Island, Greece, he decided to get a Mike Tyson henna tattoo that he'll probably be regretting for a while...

While the henna used by most professionals is a natural brown coloring that will fade in a few days, some less reputable tattooists simply use cheap black hair dye, which is advertised as black henna. Black hair dye contains paraphenylenediamine (PPD), a chemical that is banned from use on skin in the European Union because it can lead to severe burns on some people.

In 2015, Mary Bates of the United Kingdom, then 16, got a tattoo on her leg that led to similar scarring while in Turkey. She was told by doctors from St. Albans Hospital, Hertfordshire, that the scarring could stay with her for the rest of her life.

Dr. Christopher Flower, Director-General of the Cosmetic, Toiletry and Perfumery Association, warned those who seek Henna tattoos to go to reputable artists.

"Having a so called 'black henna' temporary tattoo presents a significant risk of a very nasty adverse reaction to the tattoo itself."

"It also increases the risk of either not being able to use most hair dyes in the future or having a bad reaction to them if the warnings are ignored."